Method and device for lithography-based additive production of three-dimensional shaped bodies

ABSTRACT

In a process for the lithography-based generative production of three-dimensional shaped bodies, wherein material that is solidifiable by exposure to electromagnetic radiation is present on a material support that is permeable in at least a region thereof, a building platform is positioned at a distance from the material support, material located between the building platform and the material support is heated and in the heated state is location-selectively irradiated by a first radiation source and solidified, wherein the electromagnetic radiation is introduced into the material from below through the material support that is at least partially permeable to radiation from the first radiation source, the heating of the material is performed by irradiating the material support with electromagnetic radiation of a second radiation source, wherein the material support is substantially impermeable for the radiation of the second radiation source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is the U.S. National Stage of PCT/AT2017/000056, filed Aug. 10,2017, which claims priority to European Patent Application No. EP16450019.1, filed Aug. 18, 2016, and all contents of each of theseapplications are incorporated herein by reference in their entireties.

The invention relates to method for the lithography-based generativeproduction of three-dimensional shaped bodies, wherein material that issolidifiable by exposure to electromagnetic radiation is present on amaterial support that is permeable in at least a region thereof, abuilding platform is positioned at a distance from the material support,material located between the building platform and the material supportis heated and in the heated state is location-selectively irradiated bya first radiation source and solidified, wherein the electromagneticradiation is introduced into the material from below through thematerial support that is permeable in at least a region thereof toradiation from the first radiation source.

The invention further relates to a device for carrying out such amethod.

In lithographic or stereolithographic additive manufacturingphotopolymerizable starting material is processed in layers to formshaped bodies. The layer information is thereby locally and timeselectively transmitted on the material to be polymerized either by anoptical mask, a projected image area or by scanning by laser beam. Here,fundamental distinctions are made in the choice of the exposure andstructuring methodology: on the one hand, a (dip) basin of aphotopolymerizable material can be exposed to radiation from above,wherein during production the structured object is successively immersedin the liquid material (SLA), or else a material reservoir (filledmaterial trough) is exposed to radiation from below through atransparent trough bottom, the object being withdrawn from the materialbath from above (DLP, laser stereolithography). In the latter case, theobject is structured layer by layer, whereby the respective distancebetween the object and the material trough bottom guarantees ahigh-precision layer thickness. In novel processes, this type ofstructuring can also be carried out continuously instead of in layers,in which case further special requirements must be imposed on the troughbottom.

Common to all these process methods is the high geometric quality of theadditively structured products. In addition to the geometric quality ofan object, its material quality is also crucial for technicalapplications, but also in the area of end-user products. In the case ofadditively processed plastics, known deficits manifest themselves aboveall in terms of temperature resistance (pronounced loss ofrigidity/modulus of elasticity when the temperature increases, usuallystarting at as low as 40-50° C.) or toughness (impactstrength/resistance to fatal cracking or cracking) at ambienttemperature.

Novel photopolymer systems for stereolithography processes, which allowthe production of shaped bodies with improved material quality,generally have a high viscosity and are therefore difficult to process.The high viscosity complicates, for example, the material feedconsiderably. It is therefore currently desired to use materials whosedynamic viscosity in the processing stage do not exceed the range of afew Pa·s (Pascal-seconds).

In order nevertheless to process materials with higher viscosity, it hasalready been proposed to conduct the process at elevated temperature.Even with a small increase in the process temperature compared to normalroom temperature (20° C.), the viscosity of most photopolymers decreasessignificantly. This results in a considerable enlargement of the choiceof available starting polymer substances which can subsequently lead tonovel 3D printing materials.

In stereolithography the type of process heating constitutes achallenge, especially in the conduct of processes with the materialtrough being irradiated from below, if a uniform heating of the troughcontents is to be achieved. WO 2015/074088 A2 discloses a method inwhich the heat is supplied by means of an intransparent resistanceheating at the edge of the exposure zones. The disadvantage here is thatlarge temperature gradients arise within the material trough, wherebythe process control is considerably more difficult or no homogeneousmaterial viscosity can be ensured.

WO 2016/078838 A1 discloses a method in which the heating takes placewith the aid of a transparent coating of the trough bottom that iselectrically conductive over the entire area and heats up when beingpassed by an electric current. Although this succeeds in homogenizingthe heating, however, possible heating power limits are reached quicklyand temperatures above 60° C. are difficult to maintain in continuousoperation. To make matters worse, certain transparent electricalcoatings (indium tin oxide, ITO) increasingly absorb visible lightwavelengths below 450 nm and are already completely non-transparent inthe region of near UV light. However, it is precisely this near UV rangethat is a prerequisite for efficient stereolithographic processing ofplastics. This applies in particular when undyed transparent plasticsare to be processed.

Another possibility of direct or indirect material heating isconceivable by thermal radiation with infrared rays. An advantage ofheating by means of thermal radiation is the at least theoreticallypossible, high heating power which can be delivered to the material. Thenatural absorption of at least parts of the infrared spectrum byplastics and photopolymers can represent both the advantage justmentioned but also a decisive disadvantage: A sufficient control of theheating rate as well as of the final temperature of the reactivephotopolymer to be heated is difficult to impossible. Penetratinginfrared radiation is continuously absorbed by the photopolymer andthereby attenuated. In a material bath, the exposed surface and areasdirectly below it heat up strongly, while deeper regions remain cooler.The poor thermal conductivity of the liquid starting materialscontributes decisively to an inhomogeneous temperature distribution.

In the case of heating a thin polymer layer by infrared radiation,maintaining the process temperature is a problem again: A thin layer ofmaterial cools rapidly to ambient temperature due to its extremely largesurface area in relation to its volume (heat conduction to ambient airand convection). However, the thus required continuous infraredirradiation of this surface can now also lead to a very rapid localincrease in the layer temperature, as a result of which atemperature-induced free-radical polymerization or other damage to thematerial can take place. Since the photopolymers to be processed alsobecome considerably more reactive as a result of the temperatureincrease and thus carry out individual reaction steps even in theunexposed state, at least a deterioration of the process quality overtime is to be assumed.

Also known are variants of stereolithography machines, which perform thestructuring process in a kind of furnace, whereby the entire processzone can be heated. Although this solution is technically feasible, itrequires a complex and expensive construction of the stereolithographysystem and requires high energy consumption during the process.

The aim of the present invention is therefore to provide a technicalsolution which can guarantee a controlled and homogeneous heating of thephotopolymer to be processed during the process and which can beimplemented as easily as possible in the existing process technology.

To solve this problem, the invention provides in a method of the typementioned above, that the heating of the material is performed byirradiating the material support with electromagnetic radiation of asecond radiation source, wherein the material support is substantiallyimpermeable for the radiation of the second radiation source.

The invention thus provides that two separate radiation sources areused, wherein the first radiation source provides for the polymerizationor solidification of the solidifiable material that coats the materialsupport and the second radiation source serves for the heating of thematerial support in the sense of radiant heating. The material supportis designed for this purpose so that it is transparent to the radiationof the first radiation source, so that the radiation enters the materialto be solidified, and that it is substantially impermeable to theradiation of the second radiation source. The radiation of the secondradiation source is thus absorbed in the material support and thereensures a heating of the material support, wherein the material to besolidified is heated indirectly, namely by heat transfer by heatconduction from the material support to the material to be solidified.

The selective permeability of the material support is preferablyachieved by virtue of the fact that the radiation of the first radiationsource comprises a first wavelength range and the radiation of thesecond radiation source comprises a second wavelength range, which isdifferent from the first wavelength range and in particular does notoverlap with the same.

In particular, the radiation of the first radiation source is in thewavelength range of 200-900 nm, in particular 300-400 nm or 400-480 nm,and the radiation of the second radiation source is in the infraredspectrum, in particular in the wavelength range of 900-15.000 nm.

The material support is designed so that it is transparent or partiallytransparent for the radiation of the first radiation source, inparticular in the range below 500 nm (blue, violet spectrum) or forradiation of the near to medium UV range in the range 300 nm-400 nm.This enables a location-selective and time-selective structuring of thephotosensitive material through the material support, thereby enablingthe additive manufacturing process. The selective exposure to light cantake place by means of digital light processing (DLP, area exposure of aslice image), laser (scanning of the image) or other active or passiveoptical masks.

The controlled uniform heating of the solidifiable material should alsotake place mainly by heat conduction from the material support to thematerial itself, whereby a narrow temperature process window can bemaintained over a long period of time. In this case, an infraredradiation source is preferably used to heat the material support. Thematerial support must then be largely opaque in the spectrum of theincident infrared radiation (>900 nm) or at least absorb a range of theinfrared spectrum between 900 nm and 15000 nm in order to experiencesignificant heating. In order to avoid the problems of temperaturecontrol of the photosensitive material described in the prior art, thematerial support used should preferably absorb or filter out as far aspossible all areas of the infrared spectrum used for heating, whereby aslittle as possible or no infrared radiation can pass through and thusreach the photosensitive material itself.

By the fact that the material support according to the invention isheated without contact and by radiation-induced energy transfer, it isavoided that the photosensitive (and always temperature-labile) startingmaterial is irradiated directly with infrared radiation. This has theadvantage that (in contrast to electrically conductive transparentfilms—e.g. ITO coating) high heating power can be achieved. Furthermore,the indirect irradiation can preclude early thermally-induced anduncontrolled polymerization of the photosensitive material as a resultof its own infrared absorption (and the resulting uncontrolledadditional heating). Since the heat transfer between the materialsupport and the photosensitive starting material takes place only by wayof pure heat conduction as far as possible, the maximum temperature ofthe photosensitive starting material can be controlled very preciselyvia the temperature of the material support. This works the better, thethinner the layers of the starting material are used in the process. Inaddition, the elimination of non-transparent resistance heating elements(which can be used only outside the actual exposure zone) leads, aboveall, to the fact that a homogeneous process temperature can be set andmaintained over the entire construction field or the entire materialsupport.

A preferred embodiment provides that the radiation of the secondradiation source is applied to the material support from the directionof the first radiation, so that the material support is heated frombelow.

In order to achieve uniform heating of the material support over aslarge a surface as possible, the largest possible area of the materialsupport should be irradiated by means of the second radiation source,namely in particular at least that region of the material support whichis coated by the material to be solidified. A further preferred methodprovides in this context for the radiation of the second radiationsource to be directed to the region of the material support that istransparent to the radiation of the first radiation source.

The material support can for example consist of an infrared-absorbingglass or glass laminate, which meets the above requirements and isoptionally provided on the upper and/or the lower side with specialcoatings. For example, these coatings can serve the purpose of enhancedinfrared reflection.

Preferably, a coating of the material support may be provided, whichsupports the stereolithography process itself. For example, a coatingfacilitating the layer separation by reducing the surface adhesion, suchas, e.g., a PTFE coating, may be provided. Reduced pull-off forces canalso be achieved with a silicone coating.

According to a preferred embodiment, the radiation source of the secondradiation is designed as an infrared radiation source with an emitterannealing temperature between 100° C. and 5,000° C., preferably between500° C. and 3,000° C.

Preferably, the irradiation of the material support with theelectromagnetic radiation of the second radiation source is carried outfor heating the material support to a temperature of 40° C.-300° C.,preferably 40° C.-150° C. Thereby, the solidifiable material can beuniformly heated in a simple manner to a temperature of at least 40° C.

The process according to the invention is particularly useful in thecase of solidifiable materials, which have a viscosity of at least 15Pa·s, preferably at least 20 Pa·s, at room temperature (20° C.). By theinventively achieved heating of the solidifiable material, the viscosityis significantly reduced, in particular to a dynamic viscosity of <5Pa·s.

One is faced with a high viscosity of the starting material inparticular in the processing of filled solidifiable materials (slip).Here, a sinterable material (e.g. ceramic or metal) in powder form isadded to a viscous, photosensitive resin. During curing, the curedpolymer acts as a binder. After the construction of the shaped body iscompleted, the cured polymer can be thermally removed and then theremaining filler material (e.g. a ceramic powder) is sintered togetherinto a solid structure. This method makes it possible to use all theadvantages of additive manufacturing for materials that would not besuitable for these processes. The degree of filling, i.e. the proportionof powder in the slip, is one of the most important factors regardingprocessability and material quality.

In general, pure polymers or polymer blends, as well as filled polymers(composites) may be considered as the solidifiable material. Filledpolymers (green bodies), which serve as starting objects for theproduction of ceramic or metallic products, are also included.Preferably, an unfilled photopolymerizable material or aphotopolymerizable material that is filled with a filler, in particularceramic or metal powder, may be used.

The quantity of the heat flow to the solidifiable material depends onthe temperature difference between the material support and thesolidifiable material as well as on the thermal conductivitycoefficients of the materials used. Here, the specific heat capacity andthermal conductivity, or the respective heat transfer coefficient of thematerial support and the solidifiable material are to be mentioned, andthe total area available for heat exchange is to be taken into account.In the heating of thin layers of the solidifiable material, a rapidapproximation as far as possible to the temperature of the materialsupport is to be expected. The process control can thus be done eitherby calculation and accurate knowledge of the heat flows within thesystem under consideration or simply by temperature measurement of thematerial support. The required radiant energy of the second radiationsource is controlled by a control system, which uses, for example, thetemperature of the material trough bottom as an actuating variable. Thetemperature measurement itself can be done either by means oftemperature sensors in selected areas of the material support or bymeans of contactless infrared measurement. Likewise, the layertemperature of the solidifiable material itself can be measured and usedas an actuating variable. The stereolithographic additive structuringprocess can therefore be performed as long as desired at a preciselydefined material temperature.

In this context, a preferred embodiment of the method according to theinvention provides that the temperature of the material support and/orof the solidifiable material is measured and the radiation power of thesecond radiation source is controlled in dependence on the measuredtemperature values.

As already mentioned, the construction process is preferably carried outin layers. In this case, the method can be carried out in such a waythat successively shaped body layers are formed one above the other,each by forming a material layer of predetermined thickness on thematerial support and by lowering a building platform or the shaped bodythat has at least partially been formed on the building platform intothe material layer so that a layer of the material to be solidified isformed between the building platform or the shaped body and the materialsupport, which is solidified by irradiation to form the desired shape ofthe shaped body layer.

The material support is preferably formed as the bottom of a trough thatreceives the solidifiable material. Alternatively, the material supportcan also be designed as a foil.

The described material support can also be designed to be movable, ifthis supports the layer application of the solidifiable material.

According to a further aspect of the invention, an apparatus for thelithograph-based additive production of three-dimensional shaped bodiesis provided, comprising a first radiation source of electromagneticradiation and a material support that, at least in a region thereof, ispermeable for the radiation of the first radiation source and that isprovided for supporting a material solidifiable by the action of theradiation, further comprising a building platform, which is held at anadjustable height above the material support, a first irradiation unitthat comprises the first radiation source and that is controllable forthe location-selective irradiation of material located between thebuilding platform and the material support from below through thematerial support, and a heating device for heating the material locatedbetween the building platform and the material support, characterized inthat the heating device comprises a second irradiation unit with asecond radiation source of electromagnetic radiation directed to thematerial support and that the material support is substantiallyimpermeable for the radiation of the second radiation source.

A preferred embodiment of the device provides that the radiation of thefirst radiation source comprises a first wavelength range and theradiation of the second radiation source comprises a second wavelengthrange that is different from, in particular non-overlapping with thefirst wavelength range.

The radiation of the first radiation source is, for example, in thewavelength range of 200-900 nm, in particular 300-400 nm or 400-480 nm,and the radiation of the second radiation source is preferably in theinfrared spectrum, in particular in the wavelength range of 900-15.000nm.

A further preferred embodiment of the device provides that the secondirradiation unit is arranged such that the radiation of the secondradiation source is applied to the material support from the directionof the first radiation.

A preferred embodiment of the device provides that the radiation of thesecond radiation source is directed onto the region of the materialsupport that is transparent to the radiation of the first radiationsource.

A preferred embodiment of the device provides that the material support,on the side coated by the solidifiable material and/or on the sidefacing away from the solidifiable material, carries a layer that atleast partially absorbs or reflects the radiation of the secondradiation source.

A preferred embodiment of the device provides that a temperature sensorfor measuring the temperature of the material support and/or thesolidifiable material is provided, which cooperates with a control unitfor controlling the heating power of the second irradiation unit suchthat a predetermined temperature of the material support or thesolidifiable material can be achieved and/or maintained.

A layered structure of the shaped body is preferably achieved in that acontrol unit co-operating with the first irradiation unit is designed tosolidify in successive irradiation steps superimposed layers on thebuilding platform each with a predetermined geometry by controlling thefirst irradiation unit and to adjust, after each irradiation step for alayer, the relative position of the building platform to the materialsupport so as to successively abuild the shaped body in the desiredshape.

Preferably, a movably guided doctor blade and a drive unit forreciprocating the doctor blade under the building platform are provided,in order to form a layer of predetermined thickness of the solidifiablematerial between two irradiation steps in each case, or the materialsupport itself can be movably guided under a stationary doctor blade ora coating unit.

The invention will be explained in more detail with reference toembodiments schematically shown in the drawing. Therein,

FIGS. 1 to 3 show schematic lateral sectional views of a deviceaccording to the invention in successive phases of the process sequence,and

FIG. 4 shows the layer structure of the trough bottom.

The operation of a device for carrying out a method of the presentinvention will first be described with reference to FIGS. 1 to 3 , whichshow, with the exception of the heating of the solidifiable material, adevice known per se from EP 2505341 A1. The device located in air oranother gas atmosphere has a trough 1, the trough bottom 2 of whichforms a material support and is transparent or translucent at least in apartial region 3. This partial region 3 of the trough bottom comprisesat least the extent of a first irradiation or exposure unit 4, which isarranged under the trough bottom 2. The irradiation unit 4 has a firstradiation source not shown in detail and a light modulator, with whichthe intensity can be controlled by a control unit and adjusted in alocation-selective manner to produce an irradiation field on the bottomof the trough 2 with the geometry desired for the layer to bemomentarily formed.

Alternatively, a laser may also be used in the first irradiation unitwhose light beam successively scans the irradiation field with thedesired intensity pattern via a movable mirror that is controlled by acontrol unit.

Opposite the first irradiation unit 4, a building platform 5 is providedabove the trough 1, which is supported by a lifting mechanism, notshown, so that it is held in a height-adjustable manner above the troughbottom 2 in the area above the irradiation unit 4. The building platform5 can also be transparent or translucent.

In the trough 1 there is a bath of radiation-solidifiable, in particularphotopolymerizable material 6. The material level 7 of the bath isdefined by a suitable element, such as a doctor blade, which applies thematerial uniformly in a certain material layer thickness a on the troughbottom 2. The trough 1 may for example be associated with a guide railon which a carriage is guided displaceably in the direction of thedouble arrow 8. A drive provides for the reciprocation of the carriage,which has a holder for a doctor blade. The holder has, for example, aguide and an adjusting device in order to adjust the doctor blade in thedirection of the double arrow 9 in the vertical direction. Thus, thedistance of the lower edge of the blade from the bottom 2 of the trough1 can be adjusted. The doctor blade is used when the building platformis in the raised state as shown in FIG. 1 and serves to distribute thematerial 6 evenly while setting a predetermined layer thickness. Thelayer thickness of the material 6 resulting from the materialdistribution process is defined by the distance of the lower edge of thedoctor blade from the bottom 2 of the trough 1, as well as by the movingspeed of the doctor blade.

The resulting material layer thickness a is greater than the shaped bodylayer thickness b (FIG. 2 ). To define a layer of photopolymerizablematerial, the procedure is as follows. As shown in FIG. 2 , the buildingplatform 5, on which shaped body layers 10′, 10″ and 10′″, which formthe shaped body 11, have already been formed, is lowered in a controlledmanner by the lifting mechanism, so that the underside of the lowestshaped body layer 10′″ first touches the surface of the material bath 6having the height a, then dips in and approaches the trough bottom 2 sofar that exactly the desired shaped body layer thickness b remainsbetween the lower side of the lowest shaped body layer 10′″ and thetrough bottom 2. During this dipping process photopolymerizable materialis displaced from the gap between the bottom of the building platform 5and the trough bottom 2. As soon as the shaped body layer thickness bhas been attained, the location-selective irradiation that is specificfor this shaped body layer takes place in order to solidify the shapedbody layer 10′″ in the desired shape. After the formation of the shapedbody layer 10″″, the building platform 5 is raised again by means of thelifting mechanism, which brings about the state shown in FIG. 3 . Thephotopolymerizable material 6 is no longer present in the irradiatedarea.

These steps are subsequently repeated several times in order to obtainfurther shaped body layers 10 of photopolymerizable material. Thedistance between the lower side of the last-formed shaped body layer 10and the trough bottom 2 is set to the desired shaped body layerthickness b, and then the photopolymerizable material is cured locationselectively in the desired manner.

After lifting the building platform 5 after an irradiation step, thereis a material deficit in the irradiated area, as indicated in FIG. 3 .This is due to the fact that after solidification of the layer havingthe thickness a, the material is solidified from this layer and liftedtogether with the building platform 5 and the part of the shaped bodyalready formed thereon. The thus missing photopolymerizable materialbetween the lower side of the already formed shaped body and the troughbottom 2 must be filled from the mass of the photopolymerizable material6 from the area surrounding the irradiated area. Due to the highviscosity of the material, however, this does not naturally flow backinto the irradiated area between the lower side of the shaped body partand the trough bottom, so that material sinks or “holes” can remainhere. The feeding of material into the material sink is effected by thematerial distribution effected by the doctor blade described above.

In order to facilitate the feeding of photopolymerizable material 6 intothe material sinks, a heating of the material 6 is provided according tothe invention, for which purpose one, preferably two, second radiationsource(s) 12 (see FIG. 1 ) is/are arranged below the trough 1, whoseradiation is directed to the trough bottom 2.

The at least one second radiation source 12 may be arranged next to orabove the first irradiation unit 4. The radiation, in particularinfrared radiation of the second radiation source 12 now causes auniform heating of the trough bottom 2, wherein it is largely absorbedby the latter. The photosensitive material 6 itself is only partially ornot heated by residues of the infrared radiation passing through thetrough bottom 2. These possibly occurring “radiation residues” can occurboth in the form of individual IR spectral regions or else in the formof a strongly attenuated total spectrum, but in the ideal case no longerlead to significant heating of the photosensitive material 6 itself. Therelevant heating of the photosensitive material 6 therefore takes placedirectly via heat conduction between the trough bottom 2 and thephotosensitive material 6 itself, wherein, of course, the highertemperature trough bottom 2 gives off heat to the photosensitivematerial 6.

FIG. 4 shows an example of a possible layer structure of the troughbottom 2. The base of the trough bottom 2 is formed by a partiallytransparent plate 13, which is made substantially non-transparent toradiation of the second radiation source, in particular radiation of theinfrared spectrum, and largely transparent to radiation of the lightused for structuring the photosensitive material. Examples of suitablematerials for this partially transparent plate include special opticalglasses (heat shield glasses, short-pass filters, etc.).

A silicon layer 14 of defined thickness may be applied over this plate13 in order to reduce the detachment forces occurring during theadditive construction process when the hardened layers 10 are separatedfrom the trough bottom 2. Likewise, an FEP or PTFE coating 15 or a foil15 can also be applied to this silicone layer 14 in order to furtherreduce the abovementioned detachment forces. In addition, other filmscan be incorporated in such a laminate, for example, to cause additionaloptical filter properties, or to reinforce existing filter effects.

The invention claimed is:
 1. A process for the lithography-basedgenerative production of three-dimensional shaped bodies, whereinmaterial that is solidifiable by exposure to electromagnetic radiationis present on a material support that is permeable in at least a regionthereof, a building platform is positioned at a distance from thematerial support, the material located between the building platform andthe material support is heated and in the heated state islocation-selectively irradiated by a first radiation source andsolidified, wherein the electromagnetic radiation is introduced into thematerial from below through the material support that is permeable in atleast a region thereof to radiation from the first radiation source,characterized in that the heating of the material is performed byirradiating the material support with electromagnetic radiation of asecond radiation source, wherein the material support is substantiallyimpermeable for the radiation of the second radiation source, andfurther characterized in that the electromagnetic radiation of thesecond radiation source is directed to the region of the materialsupport that is transparent to the radiation of the first radiationsource, and wherein the electromagnetic radiation of the secondradiation source thereby causes the material support and the material onthe material support to be heated uniformly so that the material isapplied uniformly on the bottom of the material support in a certainmaterial layer thickness.
 2. The method according to claim 1,characterized in that the radiation of the first radiation sourcecomprises a first wavelength range and the radiation of the secondradiation source comprises a second wavelength range, which is differentfrom the first wavelength range and in particular does not overlap withthe same, wherein the radiation of the first radiation source is in thewavelength range of 200-900 nm and the radiation of the second radiationsource is in the infrared spectrum.
 3. The method according to claim 1,characterized in that the radiation of the second radiation source isapplied to the material support from the direction of the firstradiation.
 4. The method according to claim 1, characterized in that thematerial support, on the side coated by the material and/or on the sidefacing away from the material, carries a layer that at least partiallyabsorbs or reflects the radiation of the second radiation source, or thematerial support itself consists of a building material with such anabsorption property.
 5. The method according to claim 1, characterizedin that the irradiation of the material support with the electromagneticradiation of the second radiation source is carried out for heating thematerial support to a temperature between 40° C.-300° C.
 6. The methodaccording to claim 1, characterized in that the solidifiable materialhas a viscosity of at least 15 Pa·s at room temperature (20° C.).
 7. Themethod according to claim 1, characterized in that the solidifiablematerial is heated to a temperature of at least 40° C.
 8. The methodaccording to claim 1, characterized in that the temperature of thematerial support and/or of the solidifiable material is measured and theradiation power of the second radiation source is controlled independence on the measured temperature values.
 9. The method accordingto claim 1, characterized in that the shaped body is built up in layers,wherein successively shaped body layers are formed one above the other,each by forming a material layer of predetermined thickness on thematerial support and by lowering a building platform or the shaped bodythat has at least partially been formed on the building platform intothe material layer so that a layer of the material to be solidified isformed between the building platform or the shaped body and the materialsupport, which is solidified by irradiation to form a desired shape ofthe shaped body layer.
 10. A device for the lithograph-based additiveproduction of three-dimensional shaped bodies for carrying out a methodaccording to claim 1, comprising a first radiation source ofelectromagnetic radiation and a material support that, at least in aregion thereof, is permeable for the radiation of the first radiationsource and that is provided for supporting a material solidifiable bythe action of the radiation, further comprising a building platform,which is held at an adjustable height above the material support, afirst irradiation unit that comprises the first radiation source andthat is controllable for the location-selective irradiation of thematerial located between the building platform and the material supportfrom below through the material support, and a heating device forheating the material located between the building platform and thematerial support, characterized in that the heating device comprises asecond irradiation unit with a second radiation source ofelectromagnetic radiation directed to the material support and that thematerial support is substantially impermeable for the radiation of thesecond radiation source, and further characterized in that theelectromagnetic radiation of the second radiation source is directed tothe region of the material support that is transparent to the radiationof the first radiation source, and wherein the electromagnetic radiationof the second radiation source thereby causes the material support andthe material on the material support to be heated uniformly so that thematerial is applied uniformly on the bottom of the material support in acertain material layer thickness.
 11. The device according to claim 10,characterized in that the radiation of the first radiation sourcecomprises a first wavelength range and the radiation of the secondradiation source comprises a second wavelength range that is differentfrom, in particular non-overlapping with the first wavelength range,wherein the radiation of the first radiation source is in the wavelengthrange of 200-900 nm and the radiation of the second radiation source isin the infrared spectrum.
 12. The device according to claim 10,characterized in that the second irradiation unit is arranged such thatthe radiation of the second radiation source is applied to the materialsupport from the direction of the first radiation.
 13. The deviceaccording to claim 10, characterized in that material support, on theside coated by the solidifiable material and/or on the side facing awayfrom the solidifiable material, carries a layer that at least partiallyabsorbs or reflects the radiation of the second radiation source, or thematerial support itself consists of a building material with such anabsorption property.
 14. The device according to claim 10, characterizedin that a temperature sensor for measuring the temperature of thematerial support and/or the solidifiable material is provided, whichcooperates with a control unit for controlling the heating power of thesecond irradiation unit such that a predetermined temperature of thematerial support or the solidifiable material can be achieved and/ormaintained.
 15. The device according to claim 10, characterized in thata control unit co-operating with the first irradiation unit is designedto solidify in successive irradiation steps superimposed layers on thebuilding platform each with a predetermined geometry by controlling thefirst irradiation unit and to adjust, after each irradiation step for alayer, the relative position of the building platform to the materialsupport so as to build successively the shaped body in a desired shape.16. The device according to claim 10, characterized in that a movablyguided doctor blade and a drive unit for reciprocating the doctor bladeunder the building platform are provided, in order to form a layer ofpredetermined thickness of the solidifiable material between twoirradiation steps in each case, or the material support itself can bemovably guided under a stationary doctor blade or coating unit.